ZCS 6 (amavisd 2.6.3+ and DSPAM)

I was trying to help a client upgrade their installation from 5.x to 6.x but ran into problems getting DSPAM working. After some digging, I found that Amavisd >2.6.3 changed how it handles anti-spam scanners. They've added an array of anti-spam scanners and Amavis::SpamControl::ExtProg module.

I've added the following to the amavisd.conf.in below the
%%uncomment LOCAL:amavis_dspam_enabled%%$dspam = '/opt/zimbra/dspam/bin/dspam'; line.